The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Cooling fan assemblies provide airflow to dissipate heat generated by electronic components. Cooling fan assemblies often include a motor that drives fan blades via a rotor. The speed of the rotor may be adjusted to adjust airflow and heat dissipation.
A control module controls the speed of the rotor using pulse-width modulated (PWM) signals. The PWM signals may be based on a comparison of a reference signal and a sine wave signal generated from a motor sensor signal.
The motor sensor signal may be based on signals from a Hall-effect sensor that detects changes in magnetic fields within the motor as the rotor rotates. Alternatively, the sine wave signal can be generated based on detection of back electromotive force (BEMF) from the motor. BEMF may be detected using detected voltages of motor coils and/or a centre tap of one of the coils while the motor is spinning.